Optimization Of Polyhydroxyalkanoate (PHA) Production By Burkholderia Cepacia BPT1213 Using Waste Glycerol As The Sole Carbon Source

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Date
2017-07
Authors
Mohd Zain, Nor Fauziah
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Publisher
Universiti Sains Malaysia
Abstract
Polyhydroxyalkanoate (PHA) is touted as an environmental friendly alternative to recalcitrant petrochemical derived plastics. Due to high production cost issue, waste glycerol produced from biodiesel industry has potential as cheaper carbon source for PHA synthesis by microorganisms. The objectives of this study were to optimize and scale up the production of PHA by a local isolate, Burkholderia cepacia BPT1213, from the shake flask system to a 2.5 L bioreactor system. Throughout this study, the strain was grown in minimal salt medium (MSM) supplemented with 2% (v/v) of waste glycerol (86.70% purity), a by-product of the production biodiesel from palm oil as the sole carbon source. Results showed that, in shake flask culture, the growth of the strain can build up to 1.33 g/L cell dry weight (CDW) with 22.21% of PHA content, thus giving 0.30 g/L total PHA concentration before optimization. A factorial design experiment showed that all parameters potassium dihydrogen phosphate (KH2PO4), disodium hydrogen phosphate anhydrous (Na2HPO4·2H2O), carbon-to-nitrogen ratio (C/N), initial pH of medium, and temperature significantly affected the growth (cell dry weight, CDW) and PHA content. Response Surface Methodology (RSM) using Central Composite Design (CCD) was then applied to optimize these parameters. The optimum suggested conditions were at 2.5 g/L KH2PO4, 4.5 g/L Na2HPO4·2H2O, 30 (g/g) C/N ratio, initial medium pH of 8.5 and 37 ˚C cultivation temperature, with a predicted CDW of 3.43 g/L and PHA content of 45.71% contributing to 1.57 g/L total PHA concentration. The verification experiment resulted in 3.60 g/L of CDW with 48.08% of PHA content contributing to 1.73 g/L total PHA concentration (5.77 folds improved).
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Keywords
Optimization of Polyhydroxyalkanoate , using waste glycerol
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